With the recent reappraisal of the current state of the chemical industry, chemical reactions which take place in living bodies are drawing attention and active efforts are being made in order to reproduce such chemical reactions within reactors at chemical plants, rather than in living bodies. Many enzyme-catalyzed biosynthetic reactions are carried out in living bodies in order to support life and the capability of reproducing such biosynthetic reactions within reactors is becoming an essential technology in the chemical industry because, for one thing, it readily provides those compounds which are difficult to produce by synthetic chemical reactions and, for another, it satisfies society's needs for energy conservation and a clean environment. This technology has already been commercialized in the fields of hydrolysis and isomerization.
One of the most important biosynthetic reactions is the binding reaction, and in order to carry out this reaction, adenosine-5'-triphosphate (hereinafter abbreviated as ATP) is necessary as an energy source or a cofactor. After acting as an energy source or a cofactor, ATP is degraded to adenosine-5'-diphosphate (ADP) or adenosine-5'-monophosphate (AMP). Industrial reproduction of the binding reaction therefore requires that ATP be supplied at low cost. However, ATP is a very expensive substance and the key point in the effort to commercialize the reproduction of the binding reaction is to regenerate ATP after it has been consumed into the form of ADP or AMP. In particular, successful commercialization of the binding reaction in chemical reactors will depend on converting the "lowest energy" AMP to ATP.
In fact, however, not many cases have been known of the reproduction of substances by the binding reaction as it is accompanied by ATP regeneration. One approach which has been proposed is to regenerate or replenish the consumed ATP by utilizing microbial glycolysis, and an attempt was made to use AMP as the starting material for the production of ATP (see, for example, S. Tochikura et at., Yuki Gosei Kagaku Kyokai Shi, Vol. 39, No. 6, p. 487, 1981). The AMP used in this method was not in the consumed form of ATP; rather, it was added as a separate ATP source, and, in addition, the yield of conversion from AMP to ATP was very low (see S. Tochikura et al., ibid.). Therefore, even the approach which depended on the use of microbial glycolsis turned out to be negative with respect to the possibility of regenerating ATP from the particular type of AMP which is in the consumed form of ATP.
With a view to synthesizing a useful material by continuous consumption of ATP to AMP, the concept of a bioreactor has been proposed, and it has been strongly desired to complete a system employing such a bioreactor.
In order to meet this need, the present inventors previously made concerted efforts for regenerating ATP by conversion from AMP, which is the "lowest energy" metabolite of ATP. As a result, it was found that AMP could be rapidly converted to ATP with high yield by employing converging enzymes which were produced by microorganisms having an optimal-growth temperature range of 50.degree. C. to 85.degree. C. The present inventors also found that when ATP was regenerated from AMP with the AMP/ATP mixing ratio being controlled at a specified value, substantially 100% conversion of AMP to ATP was attainable. On the basis of these findings, the present inventors continued their studies and found that by linking (1) a reaction system for regenerating ATP from AMP with (2) a reaction system for synthesizing a physiologically active substance in the presence of ATP, the physiologically active substance of interest can be synthesized from AMP which is the decomposed form of ATP at the lowest energy level. Patent was applied for in respect of this invention in the United States of America (USSN 461,308) and under the European Patent Convention (EPC Publication No. 84975) and in Canada (Canadian Pat. No. 1,194,825).
However, it was later found that when a physiologically active substance was continuously synthesized for a prolonged period by the continuous-flow process wherein the two reaction systems were linked together within in a single reactor and the reactant solution was supplied at the one end of the reactor while the product (physiologically active substance) was withdrawn from the other end of the reactor, the reactor became plugged by precipitates and the supply of the reactant solution had to be suspended. In addition, when an enzyme immobilized on a water-insoluble support was employed, the precipitates had a tendency to deposit on the surface of the support and prevent contact between the reactant solution and the enzyme, with the result that the activity of the enzyme dropped so as to reduce the yield of the physiologically active substance.
G. M. Whitesides et al reported that they devised a reactor incorporating both a reaction system for regenerating ATP and a reaction system for synthesizing a physiologically active substance with the aid of ATP and that they synthesized the following substances: glucose 6-phosphate (J. Org. Chem., Vol. 48, p. 3130 (1983)); dihydroxyacetone phosphate (ibid., Vol. 48, p. 3199 (1983)), creatine phosphate (ibid., Vol. 42, p. 4165 (1977)), NADP.sup.+ (J. Am. Chem. Soc., Vol. 106, p. 234 (1984)), ribulose 1,5-diphosphate (ibid., Vol. 102, p. 7938 (1980)) and glycerol 3-phosphate (ibid., Vol. 101, p. 5829 (1979)).
However, the productivity of the method of Whitesides et al. is very low, because a batch process is employed to produce the physiologically active substances. Furthermore, the reaction system for regenerating ATP in Whitesides et al. uses ADP, not AMP, as the starting material.